Fetal tachycardia: Mechanisms and predictors of hydrops fetalis

Objectives. This study had three objectives: 1) determine the electrophysiologic mechanisms of fetal supraventricular tachycardi at presentation and postnatally; 2) to identify the clinical and electrophysiologic predictors of hydrops fetalis; and 3) to describe the medium-term follow-up (1 to 7 years) of patients with fetal supraventricular tachycardia. Background. Fetal supraventricular tachycardi causes significant fetal and neonatal morbidity and mortality. Prenatal analysis and postnatal confirmation of fetal supraventricular tachycardi mechanisms have been limited. Methods. Supraventricular tachycardi mechanisms were evaluated by prenatal Doppler/M-mode echocardiography, immadiate neonatal surface electrocardiography and postnatal transesophageal electrophysiologic procedures in 30 consecutive patients presenting with fetal supraventricular tachycardi (17 managed preventally, 13 first managed postnatally). Results. The fetal supraventricular tachycardi mechanism was 1:1 atrioventricular conduction in 22 patients and supraventricular tachycardi with atrioventricular block (atrial flutter) in 8. At the postnatal transesophageal electrophysiologic procedure, tachycardi was induced in 27 of 30 patients; atrioventricular recentrant tachycardi in 25 (93%) of 27 and intraatrial reentrant tachycardi in only 2 (7%) of 27. Hydrops was present in 12 of 30 fetuses. Sustained supraventricular tachycardi (> 12 h) and lower gestation at presentation correlated with hydrops (p < 0.02, p < 0.05), but mechanism of tachycardi and heart rate did not. Gestational age at delivery was significantly greater in those who received intrauterine management (39 ± 1.3 vs. 37 ± 2.9 weeks, P = 0.04) despite earlier presentation (32.6 vs. 37.1 weeks). Cesarean section deliveries were reduced in the same group (3 of 17 vs. 11 of 13, P = 0.0006). Conclusions. Atrioventricular reentrant tachycardi was the pr predominant mechanism of supraventricular tachycardi in the fetus. There was high association of supraventricular tachycardi with atrioventricular block in utero and accessory atrioventricular connections. Outcome at 1 to 7 years was excellent regardless of severity of illness at clinical presentation.